1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include <cstddef> // size_t 10 #include <cwchar> // mbstate_t 11 #include <limits.h> // MB_LEN_MAX 12 #include <string.h> // wmemcpy 13 14 // Returns the number of wide characters found in the multi byte sequence `src` 15 // (of `src_size_bytes`), that fit in the buffer `dst` (of `max_dest_chars` 16 // elements size). The count returned excludes the null terminator. 17 // When `dst` is NULL, no characters are copied to `dst`. 18 // Returns (size_t) -1 when an invalid sequence is encountered. 19 // Leaves *`src` pointing to the next character to convert or NULL 20 // if a null character was converted from *`src`. 21 _LIBCPP_EXPORTED_FROM_ABI size_t mbsnrtowcs( 22 wchar_t* __restrict dst, 23 const char** __restrict src, 24 size_t src_size_bytes, 25 size_t max_dest_chars, 26 mbstate_t* __restrict ps) { 27 const size_t terminated_sequence = static_cast<size_t>(0); 28 const size_t invalid_sequence = static_cast<size_t>(-1); 29 const size_t incomplete_sequence = static_cast<size_t>(-2); 30 31 size_t source_converted; 32 size_t dest_converted; 33 size_t result = 0; 34 35 // If `dst` is null then `max_dest_chars` should be ignored according to the 36 // standard. Setting `max_dest_chars` to a large value has this effect. 37 if (dst == nullptr) 38 max_dest_chars = static_cast<size_t>(-1); 39 40 for (dest_converted = source_converted = 0; 41 source_converted < src_size_bytes && (!dst || dest_converted < max_dest_chars); 42 ++dest_converted, source_converted += result) { 43 // Converts one multi byte character. 44 // If result (char_size) is greater than 0, it's the size in bytes of that character. 45 // If result (char_size) is zero, it indicates that the null character has been found. 46 // Otherwise, it's an error and errno may be set. 47 size_t source_remaining = src_size_bytes - source_converted; 48 size_t dest_remaining = max_dest_chars - dest_converted; 49 50 if (dst == nullptr) { 51 result = mbrtowc(NULL, *src + source_converted, source_remaining, ps); 52 } else if (dest_remaining >= source_remaining) { 53 // dst has enough space to translate in-place. 54 result = mbrtowc(dst + dest_converted, *src + source_converted, source_remaining, ps); 55 } else { 56 /* 57 * dst may not have enough space, so use a temporary buffer. 58 * 59 * We need to save a copy of the conversion state 60 * here so we can restore it if the multibyte 61 * character is too long for the buffer. 62 */ 63 wchar_t buff[MB_LEN_MAX]; 64 mbstate_t mbstate_tmp; 65 66 if (ps != nullptr) 67 mbstate_tmp = *ps; 68 result = mbrtowc(buff, *src + source_converted, source_remaining, ps); 69 70 if (result > dest_remaining) { 71 // Multi-byte sequence for character won't fit. 72 if (ps != nullptr) 73 *ps = mbstate_tmp; 74 break; 75 } else { 76 // The buffer was used, so we need copy the translation to dst. 77 wmemcpy(dst, buff, result); 78 } 79 } 80 81 // Don't do anything to change errno from here on. 82 if (result == invalid_sequence || result == terminated_sequence || result == incomplete_sequence) { 83 break; 84 } 85 } 86 87 if (dst) { 88 if (result == terminated_sequence) 89 *src = NULL; 90 else 91 *src += source_converted; 92 } 93 if (result == invalid_sequence) 94 return invalid_sequence; 95 96 return dest_converted; 97 } 98